Where it's going to get tricky is that Yoshida's going to design around a hypothetical straightforward rotation, not actually tell the players what it is, and then it's going to hit the player base and they're going to tear it apart and reconstruct some max potency thing. The dev team often manages to overestimate the low-end of the player base and underestimate the high-end. I really, really wish they'd figure out how to do some kind of combat PTR with no story content in advance of this stuff, because whatever they release for SB we're going to be stuck with. They'll do adjustments but won't do major swings mid-expansion, which is a worry.
I would like this. This and the idea of Hawk's Eye giving Direct Hit bonus would be pretty great. Machinist would probably need some sort of aura effects too though to compete with bard, since bard songs still help the party (like 2% crit rate so I mean pretty much not at all?) and yeah I was kind of right since the aura is set to like 20 yalms down from 25, so maybe that reigns in movement question mark.
I'm expecting MCH will get something to compensate for the death of hyper charge, but it's hard to guess what. It'd be neat if they, say, modified Wildfire to store all damage done and actually process a small percentage of party-wide damage into the ensuing explosion, but I'm not going to get my hopes up. If the group buff is minimal enough tuning on physical ranged becomes even more important and I sincerely hope they drop the nerfed weapon damage if for no other reason than that it's annoying as hell to not get a WD out of a 5 ilvl boost when everyone else does. 20y song range is still pretty decent-- a little wider than AST expanded card range, so in theory it shouldn't be that hard to maintain--so it's probably back to Bards hopping around the battlefield again, they'll just make sure to hop in circles near the boss. If anything I could see this being more annoying for BLMs--put your leylines in the wrong spot, party moves, Bard follows them, rip bonus damage. One thing I will miss about turrets-as-regen is the ability to throw them at healers who are determined to stand next to each other on the other frigging side of the map.
It does really sound like they may just go for broke with full flexible party comp, though, which is going to make whatever meta everyone's chasing this time interesting.